This invention relates to an improved wet spinning process for fibers and more particularly to the extraction of liquid from the fibers.
In the manufacture of certain solution spun synthetic polymeric yarn, an important process step concerns extraction of the liquor material from the yarn. This is usually accomplished by either passage of the yarn bundle over rotary rolls and under water sprays or through a plurality of immersion tanks filled with water or neutralizing agents. By the latter method, it is not uncommon to utilize at least four to six tanks for maximum liquor extraction. Although the technique is highly effective, it is inherently speed limited. The yarn material must be processed through the immersion tanks at relatively slow speeds due to excessive frictional drag that tends to build up between the liquid and the bundle fibers. In addition, relatively long immersion residence time is required in order for the water or neutralizer to thoroughly wash the yarn bundle. Thus, washing low denier yarn at speeds above 500 yards per minute tends to become impractical. Finally, at the higher speeds percent liquor carry over increases steeply further reducing washing efficiency. Numerous attempts have been made to improve textile yarn washing efficiency and treatment speed but these have been limited to relatively slow process speeds since high relative velocities tend to produce frictional drag which eventually damages the product.
Accordingly, it is an object of this invention to provide a compact, highly efficient yarn wash device capable of treatment of solvent-laden yarn at high throughput rates.
Another object of the present invention is to provide a multistage solvent extraction which subjects the yarn material to substantially no tension buildup.